Shankar Bhashya on Gita- One shloka a day- 4.20

Having given up attachment to the karma-fala, he who is ever-contented, dependent on nothing, certainly does not do anything despite being engaged in karma.

Bhagvan starts this verse in order to show that for a person having the vision of akarma etc in karma etc even if the renunciation of karma is impossible due to some reason or the other and he is engaged in karmas like before, still he does not do anything because of lack of attachment in karma and the karma-fala. Because of the karmas having been burnt in the fire of jnana, his karma is akarma only.

A person is ‘learned’:-

who has given up abhimana in karma and attachment in karma-fala;

who has given up this abhimana and attachment by the jnana as spoken in 4.18;

who is thus ever contented due to this giving up i.e. who has no desire in vishayas;

who is Nirashraya i.e. dependent on nothing. Ashraya refers to that depending on which purushartha is sought to be accomplished. Thus the idea is that Nirashraya refers to the one who is devoid of dependence on any tool of achieving desired drishta or adrishta fala.

The kriyamana karma of a ‘learned’ man are in reality, in paramartha, akarma only because of him having the vision of nishkriya atman. It naturally follows that such person should renounce all karma along with their accessories.

Why so?

Because their is absence of purpose for oneself.

However, if it is impossible for such a person to renounce karma and he is engaged in karma like before either for lok-sangraha i.e. preventing people from going astray (as defined in 3.20) OR for avoiding the criticism of wise people; still he certainly does not do anything.

Why so?

Because he is endowed with the vision of of nishkriya atman.

He gets liberated:-

who, on the contrary, is the opposite of the above-mentioned one i.e. who is not engaged in karma;

in whom the atma-darshan has dawned in Brahman i.e. he understands Brahman as himself being the nishkriya pratyagatma inside everything;

who is devoid of hankering for desirable drishta and adrishta vishayas;

who has renounced all karma along with accessories due to the vision of purposelessness of karma required for achieving drishta and adrishta objects;

who is sanyasi and acts only to sustain the journey of body (i.e. life);